External connection part of semiconductor module, semiconductor module, external connection terminal, and manufacturing method of external connection terminal of semiconductor module

1. An external connection part of a semiconductor module, the external connection part comprising: a conductor having an upper surface and a lower surface; a plated layer configured to cover the upper surface of the conductor; and a nut provided on the lower surface-side of the conductor for receiving a screw penetrating the conductor, wherein the plated layer comprises a low contact resistance region overlapping a region in which the nut is provided, and a high contact resistance region that is a region except the low contact resistance region, as seen from above, and the plated layer comprises a convex portion and a concave portion on a surface in the high contact resistance region.

2. The external connection part according to claim 1 , wherein a depth from a top surface of the convex portion to a bottom surface of the concave portion is between 1.5 μm and 2.5 μm.

3. The external connection part according to claim 2 , wherein the convex portion has a width between 20 μm and 1 mm.

4. The external connection part according to claim 1 , wherein the convex portion has a quadrangular shape, as seen from above.

5. The external connection part according to claim 1 , wherein the convex portion has a circular shape, as seen from above.

6. The external connection part according to claim 2 , wherein the concave portion has a width between 20 μm and 1 mm.

7. The external connection part according to claim 1 , wherein the plated layer comprises nickel.

8. The external connection part according to claim 1 , wherein the plated layer does not include a convex portion and a concave portion on a surface in the low contact resistance region.

9. The external connection part according to claim 1 , wherein a depth from a surface of the plated layer to the upper surface of the conductor in the high contact resistance region is the same as a corresponding depth in the low contact resistance region.

10. The external connection part according to claim 1 , wherein a depth from a surface of the plated layer to the upper surface of the conductor in the high contact resistance region is greater than a corresponding depth in the low contact resistance region.

11. The external connection part according to claim 1 , comprising a pattern layer provided between the conductor and the plated layer.

12. The external connection part according to claim 1 , wherein no pattern layer is provided between the conductor and the plated layer.

13. A semiconductor module comprising: the external connection part according to claim 1 ; a case, an insulating substrate housed in the case; and a semiconductor chip electrically connected to the external connection part and provided above the insulating substrate.

14. An external connection terminal of a semiconductor module, the external connection terminal comprising: a conductor having an upper surface and a lower surface; a plated layer configured to cover the upper surface of the conductor; and a screw hole formed to penetrate the conductor and the plated layer, wherein the plated layer comprises a low contact resistance region surrounding the screw hole, and a high contact resistance region surrounding the low contact resistance region, as seen from above, and the plated layer comprises a convex portion and a concave portion on a surface in the high contact resistance region.